1. Field of the Invention
The present invention relates to rectifying diodes capable of operating at high frequency. More specifically, the present invention relates to diodes formed in a “flip-chip”—assembled integrated circuit chip. Flip-chips chips are such that the contact pads connected to the anodes and cathodes of the diodes are formed on the same side of the chip and are covered with welding balls used to attach by welding the component on a printed circuit.
2. Discussion of the Related Art
Such diodes are especially used in radio wave transceiver circuits.
FIG. 1 shows as an example a diagram of a portion of a transceiver circuit usable in portable phones and comprising high-frequency PIN diodes.
The circuit comprises an antenna 1, two transmit branches br1 and br2, and two receive branches br3 and br4. Transmit branch br1 contains a diode D1 and a capacitor C1 in series. The cathode of diode D1 is connected to antenna 1 and an electrode of capacitor C1 is connected to a signal terminal TXGSM. Transmit branch br2 contains a capacitor C2 in series with a diode D2. The cathode of diode D2 is connected to antenna 1 and an electrode of capacitor C2 is connected to a terminal CXPCF/PCF. Transmit branch br3 contains a capacitor C3 and two diodes D31 and D32 in series. An electrode of capacitor C3 is connected to a terminal RXGSM. The other electrode of capacitor C3 is connected to the anode of diode D31, the cathode of which is connected to the anode of diode D32. The cathode of diode D32 is connected to antenna 1. Receive branch br4 contains a capacitor C4 and two diodes D41 and D42 in series. An electrode of capacitor C4 is connected to a terminal RXDCS. The other electrode of capacitor C4 is connected to the anode of diode D41, the cathode of which is connected to the anode of diode D42. The cathode of diode D42 is connected to antenna 1.
Bias circuits p1, p2, p3, and p4 are connected to branches br1, br2, br3, and br4. Each bias circuit pi, i ranging between 1 and 4, comprises a capacitor Cpi. A first electrode of each capacitor Cpi is grounded. The second electrode of each capacitor Cpi is connected to a first terminal of a coil Bi. The second terminal of each coil Bi is connected to the intermediary point between the capacitor and the diode(s) of branch br1. The second electrodes of capacitors Cp1, Cp2, Cp3, and Cp4 are respectively connected to bias terminals BIAS-TXGSM, BIAS-TXDCS/PCS, BIAS-RXGSM, and BIAS-RXDCS.
Antenna 1 is connected to a common bias circuit 2. Bias circuit 2 comprises a coil Bc having a first terminal connected to antenna 1. The second terminal of coil Bc is connected to a first electrode of a capacitor Cc having its second electrode connected to ground. Two resistors R1 and R2 in series are placed between the first electrode of capacitor Cc and the ground. The intermediary point between resistors R1 and R2 is connected to a bias terminal BIAS.
When the circuit is in receive mode, for example on terminal RXGSM, terminals BIAS-TXGSM, BIAS-TXDCS/PCS, and BIAS-RXDCS are grounded and no current flows through the diodes of branches br1, br2, and br4. Terminal BIAS-RXGSM is positively biased and a current flows through coil B3, diodes D31 and D32, coil Bc, and resistors R1 and R2. Capacitor C3 behaving as a short-circuit at high frequency, the signal received on antenna 1 is transmitted onto terminal RXGSM.
When the circuit is in transmit mode, for example on terminal TXGSM, terminals BIAS-TXDCS/PCS, BIAS-RXGSM, and BIAS-RXDCS are grounded. Terminal BIAS-TXGSM is positively biased. The signal to be transmitted is transmitted from terminal TXGSM to antenna 1.
Such a circuit comprises a large number of diodes. Currently, these diodes are made in the form of discrete components. Their costs and the printed circuit surface area taken up by the diodes are thus significant.